We develop an established software which works fine on all known computers except one. The problem is to parse strings that begin with "8". It seems like "8" in the beginning of a string is a reserved character.

Parsing:
int.Parse("8") -> Exception message: Input string was not in a correct format. 
int.Parse("80") -> 0
int.Parse("88") -> 8
int.Parse("8100") -> 100

CurrentCulture: sv-SE 
CurrentUICulture: en-US

The problem is solved using int.Parse("8", CultureInfo.InvariantCulture). However, it would be nice to know the source of the problem.

Question: Why do we get this behaviour of "8" if we don't specify invariant culture?

Additional information:

I did send a small program to my client achieve the result above:

    private int ParseInt(string s)
    {
        int parsedInt = -1000;
        try
        {
            parsedInt = int.Parse(s);

            textBoxMessage.Text = "Success: " + parsedInt;

        }
        catch (Exception ex)
        {
            textBoxMessage.Text =
                string.Format("Error parsing string: '{0}'", s) + Environment.NewLine +
                "Exception message: " + ex.Message;
        }

        textBoxMessage.Text += Environment.NewLine + Environment.NewLine +
            "CurrentCulture: " + Thread.CurrentThread.CurrentCulture.Name + "\r\n" +
            "CurrentUICulture: " + Thread.CurrentThread.CurrentUICulture.Name + "\r\n";
        return parsedInt;
    }